**5. Presentation and radiographic evaluation**

The history alone can often give a great clue to the underlying cause of the carotid stenosis, once identified. Atherosclerotic disease is the most common cause of carotid stenosis, and is more prevalent in older patients. In patients with a history of head and neck cancer and exposure to radiation therapy, intimal hyperplasia and other radiation changes would be the most likely underlying cause of the stenosis, and are typically more difficult to treat compared with atherosclerotic lesions [13]. Patients involved in a recent trauma or neck manipulation may have an arterial dissection that can lead to significant arterial stenosis or occlusion [14]. All of these causes could present with or without symptoms, and although the likelihood of symptoms may be more prevalent in higher degrees of stenosis, it is important to correlate the clinical history and presentation with the radiographic findings when evaluating carotid stenosis, as this will help to drive the decisions for conservative or invasive treatment of lesions identified. Currently, the US Preventive Services Task Force recommends against screening for carotid stenosis in the general asymptomatic population [15].

patients with confirmed normal vasculature, making the positive and negative predictive

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CTA and MRA imaging modalities can often have a greater than 95% sensitivity and specificity for detecting hemodynamically significant vascular stenosis when compared with diagnostic catheter angiography as the gold standard imaging modality [18]. These non-invasive imaging studies have shown to be of benefit in screening for and following stability or progression of vascular stenosis, but it should be noted that in evaluating the accuracy of each of these imaging modalities and comparing with that of digital subtraction angiography (DSA) using an *in vitro* stenosis model, Smith et al found that the CTA and MRA studies tended to underestimate the stenosis whereas the DSA tended to overestimate the stenosis when evaluating the >70% stenosis model, while there was no significant difference between these imaging studies in the

The medical management of carotid stenosis has revolved around anti-inflammatory and antiplatelet agents as the drugs of choice. Marquardt et al studied the UK population and docu‐ mented the frequency of ipsilateral ischemic stroke in the setting of asymptomatic carotid stenosis ≥50% [20]. It was reported that with adequate medical management, the risk was 0.34% for any ipsilateral non-disabling stroke, 0.0% for severe disabling stroke, and 1.78% for ipsilateral TIA. These results would support best medical management for all asymptomatic carotid stenosis, irrespective of the degree of stenosis. Aspirin is known to have anti-inflam‐ matory properties by irreversible blockade of the cyclooxygenase (COX)-1 and COX-2 pathways of arachidonic acid metabolism. Carotid fibrous plaque formation and remodeling are influenced by several factors including MMPs secreted by leukocytes in the intima which remodel the extracellular matrix, and this results in thrombosis with vulnerable plaques in which the fibrous cap has become significantly thinned and embolic events resulting in TIA and stroke may ensue [1]. The Clopidogrel and Aspirin for the Reduction of Emboli in Symptomatic Carotid Stenosis (CARESS) trial evaluated the use of aspirin alone vs aspirin with clopidogrel in symptomatic carotid stenosis >50% and found that combination therapy reduced the frequency of asymptomatic microembolization as detected by transcranial

Several major trials evaluating asymptomatic carotid stenosis include the Veterans Adminis‐ tration Trial (VA, 1993 [22]), the Asymptomatic Carotid Surgery Trial (ACST, 1994 [23]) and the Asymptomatic Carotid Artery Stenosis Trial (ACAS, 1995 [24]). The VA trial looked at medical management alone with aspirin 650mg po BID versus combined medical management with the same aspirin dose and with CEA for asymptomatic carotid stenosis of 50% or greater in 444 men in the VA medical system. This study failed to show any statistically significant differences in clinical outcome between these two groups [22]. The ACST group evaluated the timing of CEA for patients with asymptomatic carotid stenosis of 60% or greater. Patients were treated with best medical management and the treatment group received CEA as soon as

correlation of a cervical bruit auscultated on physical exam extremely unreliable [17].

estimated stenosis when evaluating the <70% stenosis model [19].

doppler ultrasound more effectively than aspirin alone [21].

**6. Treatment options**

Several clinical trials have been performed to evaluate the patient populations who will benefit from various treatment options, including medical management, surgical intervention with carotid endarterectomy (CEA) or carotid angioplasty with or without stent placement (CAS), and also with or without distal embolic protection devices for endovascular treatments.

One publication from the Netherlands reviewed four major population based studies for a meta-analysis to determine the prevalence of moderate (50-70%) and severe (>70%) carotid stenosis in men and women at various ages [16]. The investigators determined that the prevalence of asymptomatic moderate carotid stenosis ranged from 0.2% (95% CI, 0.0% to 0.4%) in men aged <50 years to 7.5% (5.2% to 10.5%) in men aged ≥80 years, and severe carotid stenosis ranged from 0.1% (0.0% to 0.3%) in men aged <50 years to 3.1% (1.7% to 5.3%) in men aged ≥80 years. For women, the prevalence of asymptomatic moderate carotid stenosis ranged from 0% (0% to 0.2%) in those aged<50 years to 5.0% (3.1% to 7.5%) in women aged ≥80 years, while severe asymptomatic carotid stenosis for women ranged from 0% (0.0% to 0.2%) to 0.9% (0.3% to 2.4%), between these age groups. Although this data helps to understand the preva‐ lence of this condition, it can only be applied to this particular population that was studied.

Traditionally, patients who presented with stroke or TIA symptoms would undergo diagnostic catheter angiography for the diagnosis of carotid stenosis. With the advent of current noninvasive vascular imaging since the 1980's such as carotid duplex ultrasound, MRA and CTA, the most common presentation of carotid stenosis is an incidental finding of asymptomatic stenosis noted on one of these imaging studies which could be performed for a variety of reasons other than for stroke or TIA, including screening imaging studies performed to follow up clinical exam findings such as auscultation of a carotid bruit. The sensitivity and specificity of auscultation of a carotid bruit when used to evaluate for carotid stenosis are extremely poor. One study compared the sensitivity and specificity of detecting carotid or vertebral stenosis with duplex ultrasound evaluation compared with the gold standard catheter angiogram and also reviewed the presence or absence of a cervical bruit on examination. This study showed that the location and estimated degree of stenosis was accurately identified in 97% of carotid and 90% of vertebral stenosis cases with duplex ultrasound compared with catheter angiog‐ raphy, but the presence of a bruit on exam would only correctly diagnose 27.6% of patients with confirmed hemodynamically significant stenosis, and was falsely positive in 22.6% of patients with confirmed normal vasculature, making the positive and negative predictive correlation of a cervical bruit auscultated on physical exam extremely unreliable [17].

CTA and MRA imaging modalities can often have a greater than 95% sensitivity and specificity for detecting hemodynamically significant vascular stenosis when compared with diagnostic catheter angiography as the gold standard imaging modality [18]. These non-invasive imaging studies have shown to be of benefit in screening for and following stability or progression of vascular stenosis, but it should be noted that in evaluating the accuracy of each of these imaging modalities and comparing with that of digital subtraction angiography (DSA) using an *in vitro* stenosis model, Smith et al found that the CTA and MRA studies tended to underestimate the stenosis whereas the DSA tended to overestimate the stenosis when evaluating the >70% stenosis model, while there was no significant difference between these imaging studies in the estimated stenosis when evaluating the <70% stenosis model [19].
